Effect of gamma-ray irradiation on structural properties of GaAsN films grown by metal organic vapor phase epitaxy

Publication date: 15 May 2015
Source:Journal of Crystal Growth, Volume 418
Author(s): Pawinee Klangtakai , Sakuntam Sanorpim , Atiwat Wattanawareekul , Pattana Suwanyangyaun , Pornjuk Srepusharawoot , Kentaro Onabe
The effects of gamma-ray irradiation on the structural properties of GaAs1−x N x films (N concentration=1.9 and 5.1 at%) grown by metal organic vapor phase epitaxy on GaAs (001) substrates were investigated. The GaAs1−x N x films were irradiated by gamma rays with irradiation strength of 0–2.0MGy. Scanning electron microscopy and atomic force microscopy results showed that a gamma ray with a strength of 0, 0.5, 1.0, 1.5, and 2.0MGy formed holes with a density of 0.0, 8.8, 9.4, 11.5, and 11.9μm⁻², respectively, on the surface of a GaAs0.981N0.019 film with low N content. On the other hand, the irradiated high-N-content GaAs0.949N0.051 film exhibited a cross-hatch pattern, which was induced by partial strain relaxation at high N levels, with a line density of 0.0, 0.21, 0.37, 0.67, and 0.26μm⁻¹ corresponding to an irradiation strength of 0, 0.5, 1.0, 1.5, and 2.0MGy, respectively. The high-resolution X-ray diffraction and Raman scattering results revealed an increase in N incorporation and strain relaxation after irradiation. In addition, the GaAs0.949N0.051 films exhibited phase separation, which took place via N out-diffusion across the interface when the irradiation strength exceeded 1.0MGy. Based on these results, the main cause of structural change was determined to be the irradiation effects including displacement damage and gamma-ray heating.